Capsaicin enhances the non‐adrenergic twitch response of rat vas deferens

Self Cite

1 The effects of capsaicin (Cap) on contractions of ring segments of rabbit ear artery induced by field stimulation were studied.2 At low concentrations (0.3-3 gM) Cap caused transient enhancement and at higher concentrations (above 3 pM) inhibition of stimulation-induced contractions, without affecting noradrenaline (NA)-induced contractions. 3 In the continuous presence of high concentrations of Cap, rebound facilitation was observed after inhibition, and at this stage, Cap elicited less inhibition of the response. 4 Repeated application of Cap at 60 min intervals irreversibly desensitized the artery to the inhibitory effect of Cap. 5 Functional removal of the endothelium enhanced the facilitatory effect of low concentrations of Cap and attenuated its inhibitory effect. 6 Pretreatment with indomethacin abolished the facilitatory effect of Cap and enhanced its inhibitory effect, indicating that prostaglandins are involved in the action of Cap. The effect of indomethacin was more marked in preparations from which the endothelium had been removed. 7 Desensitization to substance P (SP) or substance K (SK), did not affect either the inhibitory or the facilitatory effect of Cap. 8 These results suggest that the dual effects of Cap on stimulation-induced contractions of rabbit ear artery may arise from the release of multiple mediators that act prejunctionally to modulate NA release. The stimulant effect seems to be mediated by prostanoids, while the inhibitory effect seems to be caused by a substance(s) that is not SP or SK. The possibility that the mediator is calcitonin gene-related peptide requires further study.

Section: Introduction Methodsmentioning

confidence: 99%

Dual effects of capsaicin on responses of the rabbit ear artery to field stimulation

Moritoki

Takase

Tanioka

1990

Self Cite

“…dilatation of arteries). In the electrically stimulated isolated vas deferens, neurokinin A and susbtance P enhance contractions (Moritoki et al, 1987) in contrast to the inhibitory effect of CGRP . Tissue concentrations of tachykinins are low in the rat vas deferens and substance P-like and neurokinin-like immunoreactivity were undetectable by immunocytochemistry in this tissue .…”

Section: Introductionmentioning

confidence: 98%

Demonstration of the neurotransmitter role of calcitonin gene‐related peptides (CGRP) by immunoblockade with anti‐CGRP monoclonal antibodies

Tan

Longmore

Plumpton

et al. 1994

“…More recently, studies on the effects of capsaicin on the rat vas deferens have been carried out (Maggi et al, 1987;Saito et al, 1987;Moritoki et al, 1987). The first two studies showed an inhibition of responses to electrical field stimulation by capsaicin, whereas the latter study demonstrated an augmentation by capsaicin at concentrations employed by the first two studies, although an inhibition was seen at the highest concentration of capsaicin used.…”

Section: Introductionmentioning

confidence: 99%

Modulation of neurotransmission in the guinea‐pig vas deferens by capsaicin: involvement of calcitonin gene‐related peptide and substance P

Ellis

Burnstock

1989

1 The effects of capsaicin, calcitonin gene-related peptide and substance P were studied via three parameters in the guinea-pig vas deferens: the overflow of ATP and of tritiated noradrenaline, the mechanical responses to field stimulation and the mechanical responses to exogenous noradrenaline and a4,-methylene ATP. 2 At 2 Hz, capsaicin inhibited the stimulus-evoked release of ATP, whereas it was without effect on the release of noradrenaline. At 20 Hz capsaicin did not affect the release of either of the cotransmitters. Capsaicin enhanced responses to a,fi-methylene ATP, but not to exogenous noradrenaline. 3 Calcitonin gene-related peptide, like capsaicin, inhibited the release of ATP, but not noradrenaline at 2 Hz and was without effect on release at 20 Hz. However, calcitonin gene-related peptide inhibited responses to a,,B-methylene ATP and was without effect on responses to exogenous noradrenaline. 4 Substance P had no effect on the release of either noradrenaline or ATP at either frequency. However, like capsaicin it enhanced responses to a,,B-methylene ATP and was without effect on exogenous noradrenaline. 5 These results suggest that the actions of capsaicin on the guinea-pig isolated vas deferens are mediated via the release of both calcitonin gene-related peptide and substance P. Furthermore, as capsaicin and calcitonin gene-related peptide prejunctionally modulate purinergic, but not noradrenergic transmission, this suggests that the mechanisms for the storage and release of the sympathetic co-transmitters noradrenaline and ATP may not be the same.